Tuning means for electrical musical instrument



TUNING MEANS FOR ELECTRICAL mrszcm; INSTRUMENT Filed June 16, 1952 Jan.7, 1958 R. H. PETERSON 5 Sheets-s 78 26 A 46 2 80 /y/// 61.1 511 52 7az-so ugg Jan. 7, 1958 R. H. PETERSON 2,818,759 TUNING MEANS FORELECTRICAL MUSICAL INSTRUMENT Filed June 16, 1952 1 I5 Sheets-Sheet 2 i51 Y o g v i I 1 O colviiufi J56 INVENTOR J50 i l ficlwui ffiie/won Jan.7, 1958 R; H. PETERSON 2,818,759

TUNING MEANS FOR ELECTRICAL MUSICAL INSTRUMENT Filed June 16, 1952 5Sheets-Sheet 3 IN VEN TOR.

United States Patent TUNING MEANS FOR ELECTRICAL MUSICAL INSTRUNIENTRichard H. Peterson, Chicago, 111., assignor, by mesne assignments, ofone-half to Solomon Heytow, Chicago,lll.

3 Application June 16, 1952, Serial No. 293,739

8 Claims. (Cl. 841.01)

My invention relates to the electronic production of music and includesamong its objects and advantages a practical combination of electronicsources and sound sources in which the sound is generated in a vibratingbody of air.

An electronic source of musical sound in which a tuned circuit generatesthe primary vibration, is not temperaturesensitive. An organ pipe orother sound source operating by the vibration of a body of air istemperature-sensitive, and if such an instrument is in perfect tune withan electronic instrument at a given temperature such as seventy degrees,a rise in temperature to eighty degrees will change the pitch of thenon-electronic source enough to effect serious alterations in the resultwhen both instruments are played together.

An interesting, incidental advantage of the invention is that theoperator can, when that is desired, alter the pitch of the electronicsource just enough so that when the two sources are sounded at the sametime, a desirable, combined effect commonly called celcste is.

available.

- In' the accompanying drawings:

Figure 1 is an elevation of a double-deck of eight panels, comprisingsixty-four separate, individual, musical tone sources, provided withregulating means according to the invention;

. Figure 2 is an end view of the unit of Figure 1;

Figure 3 is a diagrammatic end view, indicating the tuning flaps in anintermediate position;

, Figure 4 is an enlarged detail section on line 4-4 of Figure 1;

-Figure 5 is a diagrammatic end view of means for making the temperatureadjustment automatic;

Figure 6 is a diagram of the relationship between pitch and flap.position;

Figure 7 is a view of a complete assembly including an air-blown unitand an electronic unit; and

. Figure 8 is a partly diagrammatic view of a combined unit embodying acommon junction board.

In the embodiment of the invention selected for illustration, thechassis frame may be conventional, and includes four corner posts 10cross-connected by end pieces 12 rigid with longitudinal panels 14, 16,18, and 20 for the front side. Four more panels on the rear sideconstitute another set of identical construction. Each panel carrieseight tone producing units, each including a conventional tuned circuitof high constancy, of which the inductances are indicated at 22 inFigure 2.

Each inductance 22 is associated with a capacitor 23 connected to it byconductors 27 and 29. This is a conventional and well-known arrangementof the type illustrated in Heytow and Peterson Patent 2,649,006, wherethe condenser carries reference character 94, and the inductance is 92in Figures 2 and 4 of the patent drawings. It will be obvious that othertypes of oscillators include inductances which may be varied accordingto this invention, although the current connections ice between theinductances and capacitors and tubes are arranged in any one of a largevariety of arrangements.

Between the panels 16 and 14 I provide a structural cross-piece havingflanges 24 and a shallow trough 25 between the flanges. Abreast of thetone producing units of the panels 14 and 16 are sockets for receivingeight space discharge tubes 26. Each space discharge tube has itsinterior elements in duplicate, and performs the electronic functioninvolved for both of the tone producing units abreast of it. A slighteconomy in space is achieved by having the tubes 26 spacedlongitudinally a little less than the tone producing units, so thatthere is room at one end for a spare socket 28 for establishingconnections to other electrical units forming part of the completeinstrument. v

A duplicate center trough and set of tubes is positioned between thepanels 18 and 20.

Means are provided for high precision, simultaneous adjustment of thepitch of all the tone producing units. Beside each panel I provide apivoted flap of non-metallic material, and pieces of magnetic materialare mounted on the flap to move into and out of the magnetic field ofthe inductances 22. Thus, the flap 30 for the panel 14, when in theclosed position of Figures 1 and 2, positions two small iron plates 32,where, as best indicated in Figure 4, they lie within the space includedin the field of flux indicated by the arrows 34 and increase thepermeability of the magnetic field excited by the wind-- ing 36.

The entire inductance includes the winding 36, the supporting disk 38,the central axial tube 40, and the laminated iron core 42 carried in thesmall tube 44. Basic adjustment of the inductance is provided by movingthe core 42 axially. In the tube 40 we have illustrated a threadedextension 46 of non-magnetic material, such as brass, which may havethreaded engagement with the top partition 48 of the tube 40 and belocked in axial position by tightening a lock nut 50. The other threepivoted flaps, 52 for the panel 16, 54 for the panel 18, and 56 for thepanel 20 may be duplicates of the panel 30. It will be noted that mostof the tuned units are provided with only a single tuning strip '58rather than a double tuning strip 32. The double tuning strips areneeded in connection with the tones of lower frequency, where the totalinductance of the tuned circuit is relatively large and needs to bechanged by a greater amount than can be achieved with a single tuningstrip. As best indicated in Figure 2, the flap 30 is pivoted at 60. Theflap 52 is pivoted at 62, the flap 54 is pivoted at 64, and the flap 56is pivoted at 66. In each instance, the horizontal distance from theaxis of the inductance 22 over to the pivot for the flap is the same.

Means are provided for swingingall four flaps from the active positionof Figures 1 and 2, where the tuning strips are as close as possible tothe coils 36, up about forty-five degrees into inactive position. Amidway position is indicated in Figure 3. In such adjustments it isobviously necessary that all the units have their pitch changedsimultaneously to the same extent in all adjusted positions of theflaps. I have indicated a master plate 68 pivoted at 70. The stud 72 inthe upper left-hand corner of the master plate is connected by a pitman74 to a stud 76 in a triangular intermediate plate 78 rotating with thepanel 52 about the pivot 62. On the remote corner of the-plate 68 isstud 80 connected by the pitman 82 to a stud 84 on the narrow end plate86 on the end of the flap 30. It will be apparent that clockwiserotation of the plate 68 will produce a clockwise rotation of the plate78, and the counter-clockwise rotation of the plate 86. The lowerleft-hand corner of the plate 68 is similarly connected through pitman88 with a triangular plate 90 turning with a flap 56, and the plate 90is con- 3 nected-bypitman 92 to the heel of plate 94 turning withflap.54. Byemploying-correct geometricproportionsand angularrelationships between the parts of linkage, it is possible to have allfour flaps move in perfect unison of movement, so far as the amount ofdisplacement from the-position of Figure 2 is concerned, but with theflaps 30 and 54 turning counter-clockwise, and the flaps 52 and 56turning clockwise. In the embodiment shown, all the linkages includingthe master plate 68 are parallelograms.

The rear side of the generator illustrated is a complete replica of thefront side. The manual control means may include a conventional electricmotor 95 geared to rotate the shaft 96 and arm 98 around the axis of theshaft 96. Ann 98 is connected to one outer corner of the plate 68 by thepitman 100. For manual control, it is convenient to employ a simpletwo-way switch diagrammatically indicated at 102 in Figure and adaptedto connect the conductor 104 to the conductor 106 to actuate the motorin one direction, or to the conductor 108 to actuate the motor in theother direction. When manual control is used, it is a simple matter foran experienced musician to adjust the pitch of the electronic unit byear, so that it harmonizes perfectly with the nonelectronic units, whichmay all be connected to the same keyboard. Also, if the Celeste efiFectis desired, the operator need only change the adjustment of the plate 68so that the electronic units are either sharp or flat by a smallpercentage of a semi-tone with respect to the non-electronic units, andthe Celeste effect results.

In producing and adjusting such an assembly, all the flaps are turnedout forty-five degrees, and each individual tone source is accuratelytuned to the exact frequency desired by adjusting the core 42 andfastening it in adjusted position with the lock nut 50. It remains toadjust the tuning strips 58 and 32 so that movement to the position ofFigures 1 and 2 lowers the pitch of every individual tone source byexactly the same amount. For this purpose, all the tuning strips 58 and32 are pivotally connected to the inner face of their flaps by means offastening screws 110. By rotating the tuning strip for each individualunit about its pivot to move it farther into or out of the magneticfield, the amount by which the frequency of the entire tuned circuit islowered by lowering the. flap can be adjusted with high precision. Thus,an individual adjustment of each tuning strip 58 and, each pair ofdouble tuning strips 32 is made, so that precisely the same lowering ofpitch results in all of'the units.

It remains to make sure that when all the units are in perfect tune withthe flaps moved out to forty-five degrees, and also in perfect tune at aslightly lower pitch with the flaps in the closed position of Figures 1and 2, each individual tone unit will also be in perfect tune with allthe other tone units throughout all intermediate positions. For thispurpose, the flaps may be set in a position about halfway between theirtwo extreme positions, as in Figure 3, and the third tuning comparisonis made. Theoretically, this might involve great complications. Thelowering of the pitch of the unit by successive increments of angularmovement from the position of Figure 3 to the position of Figure 2, doesnot necessarily result in equal increments of change of pitch. Therelationship is not a linear function, but is represented by a curve ofgentle curvature. The curvature of this curve is increased bypositioning the tuning strip 32 closer to the axis of the core 42, butsuch an adjustment also increases the total effect. Accordingly, when itis found by test in intermediate position that a particular unit isworking on a curve that is a little flatter or a little less flat thanthe other units, it is necessary to readjust the curvature to fit thestandard curvature. This may be done in variousways, including: (1)change the; tuning strip 58 to one of different size, return the unit,at: Qxtreme positions, and then test at intermediate 4 position to makesure the amount of change is right; (2) bend the free end of the strip-alittle away-fronrthe flap, as indicated at 58a in Figure 2, but not farenough so that flattening the strip will stress the metal beyond itselastic limit; (3) locate part of the tuning strip material on top ofthe flap, as shown at 111 in Figure 1. Changes 2 and 3 flatten thecurve, but change 1 can either decrease orincrease the curvature.

In practice, at least with the linkage disclosed for actuating theflaps, it is found that if all the are in perfect tune at the threewidely spaced points represented by the positions of Figures 2 and 3andanother. position turned out forty-five degrees, all the otherintermediate positions will-be in substantiallyaszperfecttune-as in thethree positions tested.

A combined electronic and'non-electronic unit in which the temperatureadjustment means is as above described appears to function perfectly. Atthe beginning ofuse of" the combined unit, the organist needs to adjust;the electronic unit, which he can do very quickly by ear. Thereafter,the temperature in the room will very rarelychange the effect before hefinishes playing, to require any further adjustment, but if the sessionis-prolon-ged' and the room grows warmer or cooler, he can-makea newadjustment in a moment at'any time.

It will be apparentthat the primary tuningof each, oscillator is done atthe place ofmanufacture by meansof the adjustment screw 46. It isalwayspossible for-a service'man to alter this adjustment, but in practicethat is almost never necessary. Subsequently, still-at the factory, themuch more sensitive tuning strips 32 are adjusted and re-adjusted foreach oscillator until- -the movement of the flaps throughout theirentire range results in changes-in pitch that keep all the oscillatorsin substantially perfect tune throughout the range ofthe trimming orvernier adjustment. This trimming adjustment is the only adjustmentavailable to the playerand' will normally be used by the playeronceat-the beginning of each performance or session and occasionallywheneverthe temperature of the premises rises or falls materially beforethe session is over.

Under certain circumstances, itmay be desirable to have the unit stay intune without adjustment by theoperator. In Figure 51 have indicated aworm wheelj112' and a sector arm 114, both rigid with the shaft-96. Thesector 114 carries spaced lugs 116, each carrying an elw trical contactelement 118. A spiral piece of'bimetal'120 rigidly mounted on astationary stud 122 co-axial with the shaft 96 carries a simple arm 124,the outer insulatedhead of which lies between the electrical contacts118.

It will be apparent that if the arm 124 moves in either direction due toany change in temperature, the head 125 will contact one of the contacts118, and establish anappropriate circuit for energizing the motor 95 toturn the worm 128 through the reducing gear 97 and shift the wormwheel'1'12 and sector 114 together with. the shaft 96 in a clockwise orcounterclockwise direction as the case may be. Such a unit will keep theequipment of Figures 1 and 2 in perfect temperature adjustment at all Ifit is desired to enable the operator to produce the celeste effect atwill, it is a, simple matter to mount the lugs 116. on a slide 130 heldin the full line positionof Figure 5 by a tension spring 132. Theelectromagnet 134 may be controlled by a suitable open-and-shut switch136 on the console, and when it is energized, the slide-130 will bepulled to the left and the oeleste" effect will result until the switch136 is again opened.

As a matter of convenience, the motor wires 106 and 108 are led to thecontacts 118 through a two-pole singlethrow switch 138. This enables theoperator to disconnect the automatic temperature control whenever hewishes and depend entirely on the switch 102, It is; mechanicallydesirable to put the switch 102- under the switch 1,38, where it is notaccessible to the operatorwitb.

out opening the switch 138. Thisprevents an inadvertent short circuit.

In. assembling the inductance unit of Figure 4, the tube 40 is providedwith rivets 140 to form an abutment for the bottom fiber plate 38, and aduplicate fiber plate is put on the tube 40 and fastened in the positionoccupied in the Figure 4 by the panel. Then the winding 36 is wound inplace, and in that condition the spool and winding are held below thehole that is to receive them. The upper plate is removed, and the tube40 is thrust through the panel so that the panel itself is themechanical abutment for the winding 36 in the final, assembled position.The tube 4d may be fastened in inserted position by a conventionalpinching plate 142 commonly called a speed nut. This reduces thegeometrical separation between the tuning strips 32 and the coil to aminimum, with corresponding maximum efiectiveness of the magnetic metalin the strips 32 in changing the inductance of the parts shown in Figure4 and the frequency of the tuned circuit.

In Figure 6, the curve 144 expresses graphically the lowering of thepitch of the tuned circuit by moving the tuning strip forty-five degreesinto the position of Figures 1 and 2. It will be noted that this curveis neither a straight line nor a circle, and that its slope near theposition of zero angle, where the strip is effective to lower the pitchby three percent, is many times as great as at the forty-five degreeposition. If it were possible to have the effectiveness of the strip alinear function of the rotation of the strip as expressed by thestraight line curve 146, the sensitivity of the equipment tomanipulation of the switch 142 by the operator would be constant throughout the range. To secure a substantial equivalent of the curve 146 forthe combined assembly, so that the operator will not be embarrassed orannoyed by finding the response to manipulation many times as great whenthe flaps are at five degrees, compared with the response when the flapsare at forty degrees, the mechanical connection between the shaft 96 andthe master plate 68 is adjusted so that the arm 93 comes almost but notquite into deadcenter alignment with the pitman in the position ofFigures 1 and 2. This provides an increasingly rapid reduction in theratio between increments of movement of the master plate 63 and the arm98 as the closed position of Figure 2 is approached. This effectsubstantially corrects for the variation in sensitivity represented bythe curve 144-. The curve 144 is still an accurate presentation of thefacts so far as the angular position of the flaps themselves isconcerned, but the variable ratio of movement between the arm 98 and theplate 68 substantially cancels this irregularity and secures a curvewhich is a close approximation to the straight line curve 146, for therelation between pitch and the position of the shaft hid.

in Figure 7 l have indicated an electronic tone generating unit 148according to Figure 2, connected by conventional cables to the consoleor keyboard 150 and the loud speaker 152. The air-blown unit 154 isconnected to the same keyboard through the cable 156.

Referring now to Figure 8, I have indicated a conventional wind chest158 and two organ pipes 162 The inlet to each pipe is enclosed in anindividual box 162 and 164, provided with a conventional, electricallyactuated valve. I have indicated armatures 166 pivoted at 168, and eachcarrying a leather facing 170 to enclose the inlet opening 172 of itsbox. Electromagnets 174 are effective to rotate the armatures 166counter-clockwise to open the valves, whereupon the corresponding pipeswill sound.

Thus, the key 176, when depressed by the finger of the player, closescontacts 178 to deliver current from the bus 180 through conductor 182to the junction board 184. From the junction board, conductor 186delivers current to the electromagnet 174 for the box 164. Similarly,the key 188 closes contacts 191) to deliver current through conductor192 to another contact on the same junction board 184'. From the othercontact, conductor 19 1- delivers energy to the solenoid 174 for the box162. To incorporate an electronic unit in such a combination, I needonly provide a conductor196 to deliver current to the electronic unitthat sounds the same note as the box 164, and a conductor 198 to delivercurrent to the tone producing unit for producing the same tone as thebox 162, and so on.

When effected by an experienced and skillful person, the tuningadjustments recited are adequate to secure conformity or trackingbetween the different units within limits so close that the ear does notdetect any objectionable deviation during testing or during subsequentplaying of any number of notes simultaneously. However, it will beobvious that absolute mathematical identity is not at all closelyapproximated. This is particularly true for two reasons: (1) theinductance coils vary greatly in size and in the shape of the field offlux; and (2) because the iron cores are made as small as may be, toobtain adequate tuning, and therefore operate over wide enough fluxranges so that the permeability curve is not a straight line. It isbelieved that these factors introduce scores, if not hundreds, ofminuscule pitch deviations, each one individually too small to benoticeable. These variations are actually advantageous because, when alarge number of notes are sounded, it is these variations that give theresultant total sound output that richness or ensemble effect mostpleasing to the cultivated ear and present in any well-built, air-blownpipe organ. It is precisely the absence of these minuscule pitchdeviations, of the order of magnitude of one-tenth of one percent infrequency, that makes many electronic organs sound unnatural and harsh.

Others may readily adapt the invention for various conditions of serviceby employing one or more of the novel features involved or equivalentsthereof. It will, for instance, be obvious that if more preciseautomatic correlation between the two units is desired, the temperaturesensitive control of Figure 5 may be replaced by a sensed electroniccontrol involving a first microphone activated by the vibration in anair-filled pipe kept at the ambient temperature, and a second microphoneactivated by a corresponding tuned circuit in the electronic unit. Withthese two juxtaposed, any beat note between them can activate a relay tochange the adjustment and eliminate the beat.

Similarly, plates with holes to pass over the tubes 44, might haveadvantages in manufacture, compared with the strips 32. It is obviousthat the principles of the invention are fully applicable to any musicalinstrument susceptible to pitch variation for any reason.

The orientation of the parts shown in Figures 1 and 2 is immaterial. Asingle such assembly can be set with corner posts 10 horizontal, andrest directly ona floor or table, or several assemblies can be set oneabove the other in spaced relationship in a rack or frame, with thecorner posts 10 vertical, as in Figure 2.

As at present advised with respect to the apparent scope of theinvention, I desire to claim the following subject matter:

1. An electronic musical instrument comprising at least twoaudio-frequency tuned oscillators, a trimmer tuner adjustably associatedwith each oscillator, playeroperated control means, and meansinterconnecting said control means and said trimmer tuners for causingsimultaneous tuning adjustment of all of said oscillators in the samedirection.

2. An instrument according to claim 1 having a keyboard; said controlmeans being located adjacent said keyboard and accessible to a player;whereby manual tuning adjustments of all said oscillators can be made bythe player, substantially without interruption of the playing of theinstrument.

3. An instrument according to claim 1 in which each oscillator includesan inductance coil; and each trimmer tuner comprises a ferro-magneticelement movable between two positions; said positions being a first,outer position of minimum inductance and maximum frequency,substantially outside the geometrical confines of the field generated bysaid inductance coil; and a second, inner position of maximum inductanceand minimum frequency, at least partially within the field of saidinductance coil.

4. An instrument according to claim 3 in which each trimmer tuner ismounted for mechanically guided movement between said first and secondpositions, and said control and interconnecting means includes a singlemanual control element and connections for causing all said trimmerelements to move in and out simultaneously in unison.

5. An instrument according to claim 4 in which the tuning effect of eachtrimmer element is a continuous but non-linear function of its movement;and means for adjusting each individual trimmer element to secure,Within predetermined limits, variation, of the magnitude of the totaltrimmer tuning efiect, and variation of the degree of departure of theeffect from a linear relationship.

6. An instrument according to claim 5 in which a plurality of saidtrimmer elements are atfixed toa common supporting panel; said panelbeing pivoted to fold down toward or up away from a plurality ofinductance coils; each of said inductance coils being part of a separateoscillator; means for varying the position of each trimmer element inthe plane of said panel to vary the amount of the tuning effect; andmeans for varying the position of each trimmer in the direction of itsmovement, to vary the degree of departure from a linear relationship.

7. An instrument accordingto claim 2 combined'with temperature'sensitivemeans forming part of said interconnecting means, for automaticallyadjusting said interconnecting means to superimpose on the tuningadjustment made by the player, automatic variations in frequency equalin amount and in the same direction as the frequency changes of an organpipe due to fluctuations in temperature.

8. An instrument according to claim 7 in combination with a conventionalpipe organ; said instrument having a keyboard conventionally connectedfor playing the in strument itself, or the pipe organ, or bothsimultaneously; said temperature-sensitive means being positioned to beafiectedby the temperature obtaining in the organ pipes.

References Cited in the file of this patent UNITED STATES PATENTS2,332,076 Hammond et al Oct. 19, 1943 2,357,191 Hanert Aug. 29, 19442,437,345 Bell M Mar. 9, 1948 2,439,809 Hunter Apr. 20, 1948 2,497,661Dome Feb. 14, 1950 2,499,573 Dunn Mar. 7, 1950 2,505,182 Haller et alApr. 25, 1950 2,543,629 Hanert Feb. 27, 1951 2,562,670 Koehl July 31,1951 2,601,218 Zuck June 17, 1952 2,622,202 Gierwiatowslri Dec. 16, 19522,672,068 Hanert Mar. 16, 1954 OTHER REFERENCES Publ. 1, Physics ofMusic, by Wood, pp. 49 and 50.

